8" x 28" or 28" x 8" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 10.5" X 30.5"] Compatible with Duct 8" actual front end outer dimensions

actual front end outer dimensions are approximately 36 5/8" width X 26 5/8" height

For 12" Round Duct Opening - Spiral or Flex

+ Product Details Size – 6" x 8" or 8" x 6" is the size for the duct opening measurement only

75"H – fits a 14" X 8" duct opening

+ Product Details Size - 10"w X 22"h is the size for the duct opening measurement only

8" x 28" or 28" x 8" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 10.5" X 30.5"] Compatible with Duct 8" actual front end outer dimensions+ Product Details Perfect Fit & Easy Sizing Designed for a 8" x 28" or 28" x 8" duct opening (measured at the opening), with actual outer dimensions of 10. 5" W x 30. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 7. 75" x 27. 75" x 1" Premium Airflow Efficiency High performance cube core eggcrate design allows 95% airflow efficiency, reducing energy costs and maximizing HVAC system lifespan. Durable, Rust Free Aluminum